1. Field of the Invention
The present invention relates to an inkjet recording apparatus and a method for controlling the same.
2. Description of the Related Art
Hitherto, inkjet recording technology has been widely researched and developed for its advantages such as that a printer can be manufactured at a relatively low cost. Inkjet recording apparatuses are widely used by general public as consumer devices such as printers and multifunction devices.
In an inkjet recording apparatus, a recording head with ink discharge ports discharges ink to a medium to be recorded. With this ink discharge, ink may be attached to an ink discharge port face where the ink discharge ports are formed. When ink attached to the ink discharge face increases in its amount and contacts the ink discharge ports, troubles such that ink is not discharged (so-called a “discharging failure”), or the discharge direction of ink becomes deviated (so-called a “position error”) occur. Therefore, many inkjet recording apparatuses have wiping units for wiping the ink discharge port face.
Such wiping units include one that uses a blade made of an elastic member (so-called “wiper”) and one that uses a member such as a porous body impregnated with liquid (hereinafter may also be referred to as a “sheet-shaped wiping unit”). In particular, a sheet-shaped wiping unit is preferably used in an inkjet recording apparatus in which residues of ink attached to the ink discharge port face are firmly attached to the ink discharge port face.
In order that a sheet-shaped wiping unit has an excellent wiping result, it is necessary to wipe an ink discharge port face by using an unused portion of the liquid-impregnated member, which has not previously wiped the ink discharge port face. Therefore, most wiping units are formed to have thin and long sheet shapes, and two ends are rolled around core materials. A conveyance mechanism for conveying a sheet member impregnated with liquid is provided. With this conveyance mechanism, one or both of the core materials, or, in addition to these core materials, an additionally provided conveyance roller are rotated by using a driving unit such as a motor, thereby conveying the liquid-impregnated member. One exemplary sheet-shaped wiping unit with such a configuration is disclosed in Japanese Patent No. 4072087. In Japanese Patent No. 4072087, in order to wipe an ink discharge port face by using an unused portion of a sheet member, the sheet member is conveyed by a certain length.
By the way, in order to wipe off ink residues firmly attached to an ink discharge port face, it is effective to impregnate a liquid-impregnated member (hereinafter may also be referred to as a “wiping member”) with a wiping liquid. Roughly speaking, there are two types of methods of impregnating a wiping member with a wiping liquid.
A first method is impregnating a wiping member with a wiping liquid immediately before a wiping operation is performed by a sheet-shaped wiping unit. This method has an advantage that a highly volatile liquid can be used as the wiping liquid. On the contrary, a wiping liquid coating unit such as a wiping liquid spray becomes necessary, resulting in a disadvantage that the size and cost of the apparatus are increased.
A second method is impregnating a wiping member with a wiping liquid in advance. This method has an advantage that the size and cost of the apparatus can be reduced. On the contrary, there is a disadvantage that it is difficult to use a highly volatile liquid as the wiping liquid.
Further in the second method, when a substantially non-volatile liquid is used as the wiping liquid, a problem occurs after a sheet-shaped wiping unit is let to stand for a long time (such as about ten hours) without conveying the wiping member, as described below.
In the second method of impregnating the wiping member with the wiping liquid in advance, as described above, it is difficult to use a highly volatile liquid as the wiping liquid. Thus, it is difficult to use a wiping liquid that has water, which is most appropriate as a wiping liquid, as a main component. Therefore, in many cases, solvents with a low volatility appropriate as wiping liquids are used. However, many solvents appropriate as wiping liquids absorb atmospheric moisture or discharge moisture to atmosphere in accordance with the ambient temperature and humidity. Thus, when the sheet-shaped wiping unit is let to stand for a long time without conveying the wiping member, a rolled portion of the wiping member (hereinafter referred to as a “rolled portion”) and a portion that has not been rolled (hereinafter referred to as a “not-rolled portion”) may have a difference in moisture content of the wiping liquid. That is, the moisture content of the wiping liquid of the wiping member after the sheet-shaped wiping unit is let to stand for a long time is such that the moisture content in the rolled portion does not change much, whereas the moisture content in the not-rolled portion, which is directly exposed to the atmosphere, may greatly change in accordance with the ambient temperature and humidity. For example, when the ambient humidity is high, the moisture content of the wiping liquid in the not-rolled portion which performs a wiping operation increases. Thus, the wiping performance is not degraded. However, when the ambient humidity is low, the moisture content of the wiping liquid in the not-rolled portion decreases, resulting in degrading of the wiping performance.
In many cases, inkjet recording apparatus of the recent years are configured such that ink is discharged from ink discharge ports toward the direction of gravity (vertical direction). In such a configuration, the not-rolled portion which performs a wiping operation is substantially consequently arranged above the rolled portion in the vertical direction. Thus, when the sheet-shaped wiping unit is let to stand for a long time without conveying the wiping unit, the overall wiping liquid impregnating the wiping member moves downward due to gravity, and, accordingly, a portion of the wiping liquid impregnating the not-rolled portion which performs a wiping operation moves toward the rolled portion. As a result, the impregnating amount of the wiping liquid in the not-rolled portion which performs a wiping operation is reduced, and hence, the wiping performance is degraded.
As described above, when the sheet-shaped wiping unit is let to stand for a long time without performing a wiping operation, one or both of the moisture content of the impregnating wiping liquid, and the impregnating amount of the wiping liquid become different between the rolled portion and the not-rolled portion. Therefore, the wiping performance of the sheet-shaped wiping unit is degraded.